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ORCHID SPECIES CULTURE Charles and Margaret Baker Mesoglossum londesboroughianum (Rchb. f.) Halbinger AKA: Odontoglossum londesboroughianum Rchb. f. At the time that the other "Mexican odontoglossums" were transferred to the genus Lemboglossum, this species was moved into the single-species genus Mesoglossom . According to Halbinger (1982), "After trying very hard to fit Odontoglossum londesboroughianum into one of the established sections or genera, entirely without success, we have decided to make a new genus for this one species." ORIGIN/HABITAT: Mexico. This orchid is known only from the state of Guerrero where it grows at 3300-3950 ft. (1000-1200 m). Plants are found mostly in areas of mixed vegetation where they grow on rocks in full sun on east-facing slopes. However, plants occasionally grow epiphytically on the surface of the ground. Halbinger (1982) included excellent habitat information in the hope of assisting growers in finding suitable growing conditions. With the same thought in mind, Halbinger's extremely helpful information is included here. According to Halbinger, "The plants grow at 1,000 to 1,200 m altitude, on masses of early Cretaceous crystalline rocks, in full sun or only light shade, usually facing east. The thick, simple, whitish roots cling to the rocks, the plants growing upward in hollows or even over the smooth surface. In the growing season the plants receive the heavy rains of summer; during the dry season they are exposed to occasional mists and to the dew of early morning. They prefer well-ventilated positions, and it was observed that those plants most exposed to direct sunlight, facing east or south, flower notably more heavily than do plants in semi-shade. It is the feature of these plants that they shed their leaves at the end of October, and that when they resume growth in spring, the pseudobulbs are entirely leafless." CLIMATE: Station #76762, Chilpancingo, Mexico, Lat. 17.6N, Long. 99.5W, at 4462 ft. (1360 m). Temperatures are calculated for an elevation of 3600 ft. (1100 m). Record extreme temperatures are not available for this location. N/HEMISPHERE JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC F AVG MAX 85 87 89 92 92 88 86 86 86 87 87 86 F AVG MIN 56 58 61 64 66 68 66 66 66 64 60 57 DIURNAL RANGE 29 29 28 28 26 20 20 20 20 23 27 29 RAIN/INCHES 0.1 0.1 0.1 0.3 0.9 3.2 5.2 3.5 4.4 1.1 0.1 0.0 HUMIDITY/% N/A BLOOM SEASON * * DAYS CLR N/A RAIN/MM 3 3 3 8 23 81 132 89 112 28 3 0 C AVG MAX 29.4 30.6 31.7 33.3 33.3 31.1 30.0 30.0 30.0 30.6 30.6 30.0 C AVG MIN 13.3 14.4 16.0 17.7 18.8 19.9 18.8 18.8 18.8 17.7 15.5 13.8 DIURNAL RANGE 16.1 16.2 15.7 15.6 14.5 11.2 11.2 11.2 11.2 12.9 15.1 16.2 S/HEMISPHERE JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN Cultural Recommendations: LIGHT: 3500-5000 fc. Very bright conditions are required. Plants will adapt full morning sun, but slight shading may be beneficial at midday. Strong air movement should be provided at all times, a brisk breeze is extremely important for plants in extremely bright light. TEMPERATURES: Summer days average 86-88F (30-31C), and nights average 66-68F (19-20C), with a diurnal range of 20F (11C). The warmest season is spring when days average 89-92F (32-33C), nights average 61-66F (16-19C), and the diurnal range is 26-28F (15-16C). HUMIDITY: Reports are not available for this location. Records from other stations in the region, however, indicate that humidity probably averages 75% most of the year, with 60-65% humidity in winter and early spring. WATER: Rainfall is light to moderate during the four-five month rainy season that lasts from late spring into autumn. Amounts decrease rapidly in autumn, which is the beginning of the six month winter dry season. Cultivated plants should be watered often while actively growing, but their roots must be allowed to dry out between waterings. Water should be reduced dramatically in autumn. FERTILIZER: 1/4-1/2 recommended strength, applied weekly when plants are actively growing. Many growers prefer to use a balanced fertilizer throughout the year. Other growers use a high-nitrogen fertilizer from spring to midsummer, then switch to a high phosphate formula in late summer and autumn. Fertilizer should be stopped when leaves drop in late summer or autumn. REST PERIOD: Winter days average 85-87F (29-31C), and nights average 56-58F (13-14C), with a diurnal range of 29F (16C). Although rainfall is very low for 6-7 months in winter and spring, some additional moisture is available from early-morning dew and mist. Cultivated plants should be misted occasionally, with a rare, light watering if the pseudobulbs start to shrivel or show signs of stress. Fertilizer should be eliminated until new growth starts and normal watering is resumed in spring. New growths may be susceptible to rot, so water should kept away from the expanding young tip, especially if humidity is high so that evaporation is slow. GROWING MEDIA: New growths are widely spaced along the long rhizome, so these plants are probably more easily managed if mounted on cork or tree-fern slabs. However, mounted plants need high humidity, and during hot, dry weather, they may require several waterings a day. If humidity is low plants maybe grown in well-drained pots or baskets using a very open, fast-draining, well-aerated medium that allows the roots to dry rapidly after watering. Some use medium-sized fir bark or shredded tree-fern fiber and add chunky perlite to help keep the medium open and also retain some moisture. Including charcoal in the mix also helps hold the medium open and keeps it from becoming sour. Conditions around the roots should never become stale or soggy, and plants should be repotted immediately if the medium starts to break down. Repotting may be done just as new roots start to grow. This enables the plant to become established in the shortest possible time. MISCELLANEOUS NOTES: The bloom season shown in the climate table is based on reports from the habitat. Reports from growers indicate that cultivated plants bloom in autumn and early winter. Plant and Flower Information: PLANT SIZE AND TYPE: A rather large, sympodial lithophyte or terrestrial with growths to about 22 in. (56 cm) tall. PSEUDOBULB: 3 in. (7.5 cm) long by 1.8 in. (4.5 cm) wide. The uniformly olive-green, egg-shaped pseudobulbs are laterally compressed and develop furrows on the flattened sides as they become older. When young, each growth is partially enclosed at the base by 2 pairs of leaf-bearing sheaths. Growths are spaced as much as 3 in. (7.5 cm) apart on a long rhizome that normally grows in a straight row and the rhizome seldom divides to develop more than a single new growth each year. LEAVES: Up to 18 in. (45 cm) long by 1.8 in. (4.5 cm) wide. Each growth carries 2-3 narrowly lanceolate, sharply pointed, rather soft-textured leaves are carried at the apex of each pseudobulb. All leaves are narrowed toward the base. They are folded lengthwise along the midvein for some distance above their point of attachment. The blades on the basal sheaths are graduated in size with the lower ones being the smallest and the uppermost ones sometimes being as large as the apical leaves. The blades on the basal sheaths are quickly deciduous, usually dropping by the time the plant blooms in late autumn. All leaves are deciduous in winter or after flowering, however, and the pseudobulbs are bare when new growth starts in the spring. INFLORESCENCE: 28-39 in. (70-100 cm) long, occasionally growing to 72 in. (180 cm). The mostly erect, sometimes branched flower spike emerges from the base of the most recently matured pseudobulb along the axil of the upper basal sheath. The spike is often simple but occasionally branches. Flowers, which are carried on the upper third of the inflorescence, are arranged so that they alternate along each side of the spike. FLOWERS: 15-30. The attractive, long-lasting blossoms are 1.2-2.0 in. (3-5 cm) across. Flowers are bright golden yellow with concentric rows of reddish brown spots, streaks, or blotches on the sepals and petals and sometimes on the base of the lip. The sepals are sharply pointed at the apex, widest in the middle, and somewhat narrowed at the base. The dorsal sepal, which arches forward over the column, is 0.5 in. (1.3 cm) long by 0.3 in. (0.8 cm) wide. The oblique lateral sepals are 0.6 in. (1.5 cm) long by 0.3 in. (0.8 cm) wide and open fully. The large, rectangular to egg-shaped petals have rounded tips, are 0.5 in. (1.3 cm) long by 0.5 in. (1.2 cm) wide, have undulate or wavy margins, and curve forward somewhat toward the tip. The large, 3-lobed lip is about 1.1 in. (2.8 cm) long by 1.2 in. (3 cm) wide across the spreading, kidney-shaped midlobe. The base of the lip, which is not clawed, is attached directly to the base of the column. The very small, erect, pointed lateral lobes at the base of the lip are separated from the midlobe by a long, narrow isthmus. The widely spread midlobe has slightly ruffled margins and a shallow, V-shaped notch in the center at the apex. The callus at the base of the lip is yellow and white with reddish brown markings. It is shaped like half a bowl opening toward the base. The slender, arching or bow-shaped, wingless, yellow column is about 0.6 in. (1.4 cm) long. HYBRIDIZING NOTES: N/A. REFERENCES: Halbinger, F. 1982. Odontoglossum and related genera in Mexico and Central America. Orquidea (Méx.) 8(2):155. Hamilton, R. 1988. When does it flower? 2nd ed. Robert M. Hamilton, 9211 Beckwith Road, Richmond, B.C., Canada V6X 1V7. Hawkes, A.  1987. Encyclopaedia of cultivated orchids. Faber and Faber, London. PHOTOS/DRAWINGS: Halbinger, F. 1982. Odontoglossum and related genera in Mexico and Central America. Orquidea (Méx.) 8(2):155. Copyright 1998, Charles O. Baker and Margaret L. Baker Sheet version 37851031 ......................................................................... Please remember that this sheet is for your use only, and though it was provided free of charge, it may not be reproduced or retransmitted in any way without permission. ......................................................................... __________________________________________________________________________ "Orchid Species Culture" Charles & Margaret Baker, Portland, Oregon USA Orchid Culture & Pollination site http://www.orchidculture.com email <email@example.com> __________________________________________________________________________ "Orchid Species Culture Vol. 1 - Pescatorea, Phaius, Phalaenopsis, Pholidota, Phragmipedium, Pleione" 250 pages of culture information. 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